The present invention is directed to heat shrinkable film packages, and specifically to a one-way valve for evacuating such packages during the heat shrinking step of the packaging operation.
Heat shrinkable films are employed in packaging a wide variety of food and non-food items. Generally, most food products require a package which completely encloses the product. While some foods require packaging materials having oxygen barrier properties, nearly all foods require a complete, coherent covering which protects the underlying product from environmental contaminants.
Conversely, many non-food products are not particularly sensitive to exterior contamination. For non-food products such as games, compact discs, textiles, etc., the outer film overwrap merely serves as a dust cover or, as is particularly the case for software, evidence that the package has not yet been opened. In non-food products packaged in a heat shrinkable film, a hole or perforation is often provided in the film. The hole is formed in the film either prior to or during the packaging process to allow air trapped within the sealed film to escape during the heat shrinking step.
With a few minor exceptions, the presence of such perforation in food packages is not acceptable. Thus, food products must be packaged in a more complex shrink film packaging operation than that employed for packaging non-food products. Typically, food products require that the heat shrinkable packaging film is first formed into a pouch or bag into which the product is placed. The bag or pouch is then evacuated prior to sealing and heat shrinking. In addition to increased expense, such additional packaging steps provide an increased opportunity for film waste and packaging failure.
Accordingly, there is a need in the art for an apparatus and method which will allow for the packaging of food products in a simplified manner, similar to that employed in the packaging of non-food products, without leaving an opening which may result in contamination of the food and without leaving any void or opening that exposes the underlying portions of the food product to the atmosphere.
The present invention is directed to a shrink film package which includes a product, at least one web of a shrink film wrapped about the product, at least one seal defined in the shrink film enclosing the product, and a polymeric valve sealed to the film at the seal. The valve is comprised of a tube of film having a first end extending into the package, a second end extending out of the package, and an intermediate portion within the seal. The valve further includes an exterior surface and an interior surface, wherein the exterior surface comprises a sealable polymeric material whereby the intermediate portion of the exterior surface is sealed to the shrink film at the at least one seal and wherein the interior surface comprises a nonsealable material at least at the first end and the intermediate portion thereof.
The present invention is also directed to a method for packaging a product which includes the steps of
a) wrapping the product in at least one web of a heat shrinkable film;
b) subsequently sealing the heat shrinkable film thereby enclosing the product;
c) providing a polymeric valve comprising a tube of film sealed to the heat shrinkable film at a sealed portion of the heat shrinkable film such that a first end of the valve extends into the area enclosing the product, a second end extends out from the heat shrinkable film, and an intermediate portion is contained within the sealed portion of the heat shrinkable film, the valve further comprising an exterior surface and an interior surface, the valve being sealed to the heat shrinkable film at the intermediate portion of the exterior surface thereof and the interior surface comprising a nonsealable material at least at the first end and the intermediate portion thereof; and
d) heating the heat shrinkable film thereby shrinking the film about the product,
whereby simultaneously with the heat shrinking step, air surrounding the product is vented through the polymeric valve.